Insert and reduced diameter locking ring therefor



April 17, 1956 J, os 2,742,074

INSERT AND REDUCED DIAMETER LOCKING RING THEREFOR Filed March 9, 1951 2 Sheets-Sheet 1 J4 Fr L 10 v lL// L/ Z I (V/ V /7 r L /1 I I 1/ 1 I V 44 'T 1 INVENTOR.

JOSEPH ROSA/v 6 6 ATTORNEYS.

April 17, 1956 J. RosAN 2,742,074

INSERT AND REDUCED DIAMETER LOCKING RING THEREFOR 2 Sheets-Sheet 2 Filed March 9, 1951 INVENTOR.

16 a/OSI'PH Pas/w a I 6 ATTORNEYS.

United States Patent INSERT AND REDUCED DEAMETEP. LOCKING RING THEREFOR Joseph Rosan, South Gate, tlalif.

Application March 9, 1951, Serial No. 214,824 2 Claims. (Cl. 151---41.73)

This invention relates generally to helical knife blade mounting devices, and more particularly to a device of this class which incorporates a helical blade for use in wood,- plastic and similar materials, plywood, combinations of wood and plastic ply materials, textile base phenolic (plastic) materials, phenolic impregnated wood and plywood materials, etc.

This application is a continuation-in-part of my copending patent application for Knife Edge Screw, Serial No. 141,253, filed January 30, 1950, now abancloned.

The general object of the invention is the provision of an improved device of this class for use in woodlike materials.

A more particular primary object is the provision of a novel form of screw thread in the form of a helical knife blade which will so enter the wood (or other material) as to greatly reduce the disturbance of the wood structure, thereby increasing very materially (up to several hundred percent) the strength of the installation against tension stresses.

The present invention consists, in its usual typical form, of a straight cylindrical shank around which is formed a helical blade element which may be described as having knife-edge characteristics. This knife blade is sulficiently sharp at its crest, and its included angle is sufliciently acute as to penetrate or separate the wood by a unique knifing or slitting action. The helical element knifes between the wood fibers in contradi'stinction to the crushing, swedging, mashing and general breakdown of the wood structure caused by the threads of the conventional wood screw. The helical blade of the invention must, of course, displace and compact the wood fibers to a degree, but it does not substantially preload the wood, and the weakening ef feet is minor and qualitatively different from the wood fiber deflection and maceration wrought by the conventional wood screw. Everyone is familiar with the crumbs of wood resulting from installation of a conventional wood screw, such crumbs falling from the screw hole and being found impacted between the threads when the screw is removed. The helical blade of the present invention does not produce such wood crumbs when driven into and removed from a piece of wood, but rather, knifes cleanly in between the wood fibers, and comes out entirely clean, with no evidence of wood crumbs.

While my present application may be employed in the manner of a wood screw, it has particular application as a mounting device for the attachment of various members to sheet wood structures or wood-like structures, whether actually wood or plywood, or combinations of wood and plastic materials, or textile base plastic, such as phenolic materials, a phenolic impregnated wood or plywood materials. When employed as a mounting device, my invention is provided with an exi ternally threaded stud or an internally threaded socket ice 2 or bore of different pitch than the helical blade, and is preferably so arranged as to provide a shoulder which seats flush in the wood structure in which it is fitted.

An important feature of my invention is the arrangement of a helical knife blade on a cylindrical shank which projects without reduction in diameter beyond the helical blade. like structure a hole forming a sliding fit around the shank, the mounting device may be guided in accurate coaxial relation and the helical blade caused to track properly in the path established by its leading or cutting edge.

Another important feature of my invention involves a modified construction wherein an end of the shank is' provided with axial serrations and a locking ring having internal and external serrations is employed, the serrations. of the locking ring being located within the projected area of the helical knife blade and adapted to broach their way into the surrounding material. The hole or bore, receiving the mounting and its locking ring, need not be counterbored, for the slit cut in the surrounding material by the helical blade does not damage the material in any way to prevent adequate interlocking of the serrations.

The invention will be best understood by reference to the following detailed description of an illustrative embodiment thereof, reference being had to the accompanying drawings, in which:

Figure 1 is a diagram showing the form of the hel- Figure 5 is an end view of the mounting member shown in Figure 4, illustrating the slitting convolution of the helical knife blade.

Figure 6 is a reduced elevational view of a mounting member showing an integral threaded stud extending therefrom.

Figure 7 is an end view of a. modified form of my mounting member, utilizing a locking ring.

Figure 8 is an elevational view thereof with the lockingring in section and the mounting member installed in a plywood body. I

Figure 9 is an elevational view of my invention embodied as a screw member for attaching a plate to a plywood body.

Reference is first directed to Figures 1 and 2 showing the helical knife blade, employed in the exercise of my invention. Numeral 10 designates a straight cylindrical shank and numeral 11 the helical knife blade element mate outside limits of .3OP and .40? so that Fr corre spondingly varies from .70? to .602. This provision leaves adequate room between successive convolutions for a substantial area of completely undisturbed wood.

In order to achieve-the knife-like characteristics, the

helical blade has an unconventionally small included Thus, by providing in the wood or woodave-2,024

angle A, which angle is preferably about 22 at which the optimum benefits of the invention are achieved. Angles as great as 30, and as low as ll", will accomplish some of the benefits of the invention, but'are at about the outside limits. These values are to be contrasted with the 60 or greater included angle of the conventional wood screw thread.

In order for the helical blade to be adequately strong at its crest, the crest is preferably not formed with an absolutely sharp cutting edge, but with crest flats id of width dimension F of the order of thousandths of an inch, this being accomplished by reducing the theoretical blade height H to an actual basic blade height h. The maximum crest flat dimension F for most materials is around .01", and this dimension is usually, for best performance, in the approximate region of .004" to .006".

With such a dimension, the crests are suihcicutly sharp to knife readily into the wood.

It will be seen that the blade angie A, the crest fiat dimension F, and the actual blade height h are interrelated with one another, and in the preferred embodiment, for a selected included angle A of'22, the actual or basic blade height h is made .775H, giving a crest flat dimension F of (H-h) tan A. In terms of helical blade pitch P, in the preferred exemplification of the invention, the theoretical blade depth H is .9296P, and the actual or basic blade depth 11 is .7200P, these dimensions assuming, of course, an angle A of substantially 22. In other words, the actual blade depth [1 is equal to approximately three-fourths of the blade pitch P. The dimension 12 may however vary between the approximate outside limits of .6500? and .SOOOP.

It should be observed that the unconventionally small included angle of the present helical blade, in combination with its relatively sharp crest, results in a blade height h which is considerably greater than found in the threads of ordinary wood screws, and that the helical bladeof my invention accordingly has a materially increased bearing area against the wood structure when subjected to axial stress. Materially enhanced ultimate strength is thus gained from this factor alone.

The following table gives design data in accordance with the invention, corresponding to screws of conven tional sizes:

Shank diameter or nominal size Dimensions and tolerances .2300 .2000 .3300 .4050 .034 M111. 2330 .2030 .3270 .4000 .0300 To1 0030 0030 0030 .0050 .0050

i/iaii er .1040 .2100 .2500 .3750 .5150 Min. .1010 .2130 2410 .3700 .0100 T01 .0030 .0030 0030 .0050 .0050

Pltl ibl d in inches .05550 .05550 .00250 .08333 Bas e di blah; .03550 .03550 .04000 .05333 Crest 00452 .00452 .00508 .00008 h fblade 0 aciii iiii iiui .04000 .04000 .04500 .05900 Reference is directed to Figures 4 and 5. In the embodiment of my invention, herein illustrated, the shank 10 is cylindrical and of uniform diameter throughout.

The shank protrudes beyond one end of the helical blade 11 to form a pilot end 15. The extremity of the pilot end may be provided with a slight chamfer 16. The end convolution of the helical blade, adjacent the pilot end, gradually reduces in height to form a kmfing convolution 17 which slits its way into the wood or analogous material without materially damaging or reducmg the strength thereof, as will be brought out in more deta1l hereinafter. The construction shown 1n Figures 4 and 5 is provided with an internally screw threaded bore 18 and the upper end of the shank opposite from the pilot end may have a screw driver slot 19. It will be observed that the shank it} is of such diameter as to fit slidably in a bore B formed in plywood W or wood-like material. Consequently, the pilot end 15 'uides the knifing convolution of the helical blade so that only a single helical cut is made as the shank moves in a truly axial direction in the bore B.

Reference is now directed to Figure 6. The construction hcre illustrated is the same as Figures 4 and 5, with the exception that a screw threaded stud 20 is provided in place of the internally screw threaded bore 18. It should be observed that the pitch of the screw threads 13 or 20 is different from (preferably less than) the pitch of the helical blade ii. With this arrangement, the device on receiving a screw or nut for attachment of a member to the material in which the device is mounted, locks the device in place.

Reference is directed to Figures 7 and 8. In this construction, the shank it) is provided at its end opposite from the pilot 15 with a reduced neck portion 21, the extended end of which is provided with axially directed serrations 22. The serrations 22 mesh with the internal serrations 23 of a locking ring 24. The locking ring is provided with external serrations 25 which are adapted to breach axially into the bore B which receives the shank. The locking ring is provided with a pilot portion equal in diameter to the bore B to aid in placement of the locking ring.

It will be observed that the helical blade 11 does so little damage to the surrounding material that the external serrations of the locking ring may broach into the region through which the helical blade has passed. In other words, there is no need to counterbore the outer end of the bore B in order to receive the structure shown in Figures 7 and 8. This is of primary importance as the cost of counterboring can be an important factor.

Reference is directed to Figure 9. in this arrangement, my mounting device is shown as a screw with a head 27. There may be a section betweenv the helical blade 11 and the head 27 in which the shank has a diameter equal to the outside diameter of the helical blade as indicated by 28. It should be observed that the helical blade 11 makes possible the construction of a screw of extremely short axial length. Consequently, my mounting or fastening device may be used in relatively thin plywood or similar material and yet provides adequate holding power.

An installation utilizing my invention has unprecedented strength against tension stresses. in a comparative test, a No. 10 wood screw installed in dry five-ply Douglas fir wood panel material failed under a tension load of around lbs., while a helical blade in accordance with the present invention, on a shank of comparable size, held up to tension loads of 418 lbs. to 500 lbs. or better.

Figures 2 and 3 are of particular interest, being taken from enlarged photographs of sections out through an installed mounting device made in accordance with the invention (Figure 2) and in accordance with prior practice (Figure 3).

In Figure 2, the strain lines 30 of the wooden material 31 will be seen to be substantially or entirely undisturbed for a considerable area between successive blades,

and to be only slightly deflected immediately adjacent- The strainlines almost meet between the threads and ture.

curve generally downward. The result is that the wood stress allowable has been greatly reduced by the extreme disruption of wood fiber and by the general maceration and extreme deflection of the wood fibers.

The invention thus accomplishes a unique entry of the blade into the wood structure, severing and parting the fibers, but securing an anchorage therein without rupture or breakdown of the wood and without substantial preloading, compression, or deflection of the wood struc- That is, the helical blade is sufliciently thin to cut or part the wood fibers in the manner of a knife, as distinguished from the mashing and maceration caused by the traditional wood screw. In so doing, the invention accomplishes a unique and highly advantageous result that is qualitatively distinguished from known wood screw behavior.

Having fully described my invention, it is to be understood that I do not wish to be limited to the details herein set forth, but my invention is of the full scope of th appended claims.

I claim:

1. A removable mounting insert member, comprising: a cylindrical shank having an axially serrated end of relatively reduced diameter; a helical knife edge blade formed on the exterior of said shank, the convolution of said blade most remote from said axial serrations diminishing in height and forming a slitting element; and a locking ring having internal serrations mating with the serrations of said shank and having external serrations disposed within the axially projected boundaries of said helical knife blade.

2. A mounting device adapted for insertion in a bore of uniform diameter formed in a body of relatively soft material, comprising: a cylindrical shank member adapted for rotating sliding fit in such bore and havingan end forming a mounting face adapted to be set flush with the surface of such body of material; a helical knifeedged screw thread on the exterior of said shank member comprising successive turns having substantial cylindrical sections of said shank disposed therebetween and adapted to cut a helical path along the wall of such bore to secure said shank member in such bore, said flush face end of said cylindrical shank member being reduced in diameter and provided with peripheral axial serrations of an outside diameter smaller than the root diameter of said screw thread; and a locking ring, said locking ring having internal axis serrations adapted to interlock with the serrations of said shank and having external peripheral axial serrations of less diameter than the diameter of the crest of said screw thread, thereby to interlock with material surrounding such bore within the axially projected area of said screw thread to prevent turning of said shank member.

References Cited in the file of this patent UNITED STATES PATENTS 434,809 Rogers Aug. 19, 1890 440,334 Rogers Nov. 11, 1890 2,121,193 Hanicke June 21, 1938 2,380,724 Crooks July 31, 1945 2,400,348 Greene May 14, 1946 2,407,904 Rosan Sept. 17, 1946 2,457,180 Rushing Dec. 28, 1948 OTHER REFERENCES Iron Age of February 2, 1888, page 203. 

